Although the concept that calcium is a prime intermediate in "stimulus-secretion coupling" is now a scientific truism, the sequence of events triggered by the transient increase in cell calcium requires elucidation. One approach to characterizing the nature of calcium's role in secretion is in terms of possible interactions with other putative mediators. Cyclic nucleotides, more specifically cyclic AMP and cyclic GMP, as well as prostaglandins have been proposed as possible mediators of secretion. The major thrust of this project is to elucidate the mode of action of calcium on the secretory process by investigating the interactions of calcium, prostaglandins and cyclic nucleotides on ACTH-induced corticosteroid release from trypsin-dispersed adrenocortical cells of the cat. BIBLIOGRAPHIC REFERENCES: Warner, W., and Rubin, R.P. Evidence for a possible prostaglandin link in ACTH-induced steroidogenesis. Prostaglandins 9: 82-95 (1975). Warner, W., Laychock, S.G., and Rubin, R.P. Prostaglandins as mediators of adrenal steroidogenesis. Abstr. Presented at Int. Conf. on Prostaglandins; Florence, Italy; pp. 193-194; May 26-30 (1975).